The present invention relates to a developing device and an image forming apparatus including the developing device.
In a conventional image forming apparatus of an electro-photography type such as a printer, a facsimile, a copier, and the likes, an image is formed through a charging process, an exposure process, a developing process, a transfer process, a fixing process, and a cleaning process. In the developing process, after a static latent image is formed on a photosensitive drum as an image supporting member, a developing unit as a developing device develops the static latent image using toner as developer, thereby forming a toner image.
In the conventional developing device, in order to reduce a size and a cost of the printer, toner formed of one non-magnetic component is used. In the conventional developing device, a developing roller is disposed to abut against the photosensitive drum. Further, a toner regulation blade is pressed against the developing roller for forming a thin layer of toner on the developing roller. Further, the conventional developing device includes a toner supply roller formed of a foam member for supplying toner to the developing roller and scraping off toner on the developing roller not used in the developing process, an auxiliary roller for supplying toner to the toner supply roller, and the like. (Refer to Patent Reference)    Patent Reference: Japanese Patent Publication No. 11-15246
In the conventional developing device described above, when an image is continuously formed using only a small amount of toner, that is, an image with a low density is continuously formed, toner on the developing roller and the toner supply roller tends to be excessively charged to a large extent. As a result, a stain may be occurs on the photosensitive drum in a non-image forming area thereof.
In view of the problems described above, an object of the present invention is to provide a developing device and an image forming apparatus having the developing device capable of solving the problems of the conventional developing device and preventing a stain form occurring on an image supporting member in a non-image forming area thereof.
Further objects and advantages of the invention will be apparent from the following description of the invention.